Our lander’s asleep

http://blogs.esa.int/rosetta/2014/11/15/our-landers-asleep/

by jonnyscholes • 12 years ago

392 160 12 years ago

blogs.esa.int

valevk2• 12 years ago

What kind of data did the lander gather, and will it be open to the public?

vixen992• 12 years ago

It had better be given that the public paid for it at a minimum cost of 1.4 billion Euros for the strictly European input.

sz4kerto• 12 years ago

It will be given to the public -- in contrast to 99% of scientific research results published by private companies like Elsevier making you pay $30 per article (or less, doesn't matter: you must pay to get the results of a research funded by you).

Edit: most of it will be, not everything, as I've just found out.

dingaling• 12 years ago

Much of the Rosetta data is under embargo, because the instruments were not paid for by ESA but private organisations like Max Planck Institute.

Hence the paucity of hard data released to the public; the organisations have first dibs on the data to make their money back through publications and in attracting research funding.

As an example: http://www.mps.mpg.de/1979387/MPS-Beteiligungen_an_Rosetta

Basically, ESA provide the bus on which the science kit rides.

As an EU tax-payer I've raged against this in the past but that's just the way it is.

Source: direct question on this matter that I put to an ESA PR at a public lecture about Rosetta.

danmaz743• 12 years ago

Yes, it would have been much much better for us Europeans to use that money to subsidize our agriculture a bit more... /s

Maxious• 12 years ago

The data should appear on http://www.sciops.esa.int/index.php?project=PSA&page=rosetta and http://pdssbn.astro.umd.edu/data_sb/missions/rosetta/index.s... and http://nssdc.gsfc.nasa.gov/nmc/datasetSearch.do?spacecraft=R...

The lander data includes infrared imagery, x-ray spectroscopy results, electrical conductivity measurements, temperature readings (from harpoons), acoustic data, gas analysis and magnetometer data http://nssdc.gsfc.nasa.gov/nmc/experimentSearch.do?spacecraf...

valevk2• 12 years ago

Thanks for the references! Do you happen to know when the first results (verified interpretations of the data) are usually published after such experiments?

anvandare• 12 years ago

Anthropomorphizing machines somehow always manages to twang my emotional snares. http://xkcd.com/695/

Good night, little lander. Hope you dream of electric sheep.

Pyrodogg• 12 years ago

If you like that xkcd, this'll twang a few more heartstrings.

Imposter by The Doubleclicks https://www.youtube.com/watch?v=pHU67s5tOSA

codeonfire• 12 years ago

When did machines begin tweeting as themselves? I find it odd as there are usually lots of tweets that no person would make such as "scientists are sending commands to repair my body." or "soon technicians will install new parts into me."

IndianAstronaut• 12 years ago

Welcome to the world of PR.

prawn2• 12 years ago

This is one way you take science to the masses. I think giving each Philae instrument its own Twitter account is a great idea.

DodgyEggplant• 12 years ago

http://www.youtube.com/watch?v=ayM68-4EioY#t=925

mercer• 12 years ago

The first bit of Wall-E had exactly that effect on me. I think it's amazing how animators can make inanimate objects so expressive.

jacquesm• 12 years ago

Wall-E is absolutely amazing in that way. My little ones have a total crush on him and I must have seen the movie about 400 times or so. I think I know the dialogue by heart and I still like to look at it every now and then to appreciate the skill of the animators.

Symmetry• 12 years ago

And I'm sure most people here saw this compilation for Philae, but if you didn't: http://xkcd1446.org/#0

ThePhysicist2• 12 years ago

“Each night, when I go to sleep, I die. And the next morning, when I wake up, I am reborn.” - Mahatma Gandhi

Let's hope it will wake up and be reborn.

The chances for this seem not that bad, since the comet will heat up considerably as it approaches the sun, which will make it unnecessary to preheat the interior of Philae before starting to charge the batteries, while at the same time increasing the solar power reaching the panels (due to the sun being closer), so the lander might actually generate enough power to recharge the batteries and come alive again. Let's keep our fingers crossed.

raverbashing• 12 years ago

They also managed to rotate the lander so it gets more sunlight

ThePhysicist2• 12 years ago

Yeah right, let's hope this helps as well! Of course there's the possibility that the panels will get more sunlight as the angle of the comet's rotation axis changes respective to the sun.

maaku2• 12 years ago

That's one of the most scary quotes ever. Way to write a horror story in 2 sentences.

blrgeek• 12 years ago

If you've never thought about sleep that way, you should be scared! How do you know the person who woke up this morning is the same person who went to sleep last night?

bitwize• 12 years ago

Do not go gentle into that good night, Philae. Rage, rage against the dying of the light.

shdon• 12 years ago

You made me look up that poem. I hold you responsible for the tears it brought.

stinos2• 12 years ago

Everytime I read about tech like this I cant help but wonder What kind of mainboard does this run? What CPU? What temp spec? what OS does it run? What is the main laguage? Would it use open source code?

Anyone has a clue or educated guess?

edit thanks to all answers provided, exactly the info I was looking for! And very interesting as well.

pjmlp• 12 years ago

Most likely Ada, C or C++ with very strict code guidelines, which even make C feel like Ada.

Alongside real time OS like VxWorks, QNX, Aonix, ....

There was a presentation at CppCon about Mars Rover.

https://www.youtube.com/watch?v=3SdSKZFoUa8

fjarlq• 12 years ago

Some details:

http://space.stackexchange.com/questions/593/on-board-comput...

Note that the RTX2010 uses Forth:

http://en.wikipedia.org/wiki/RTX2010

acqq21• 12 years ago

Regarding the power source, and why the mission depended on only solar energy:

"Why was RTG (Radioisotope thermoelectric generator) not used in Rosetta mission?"

https://news.ycombinator.com/item?id=8610585

Only US and Russia have the technology.

duckson• 12 years ago

I don't know about Philae/Rosetta's hardware in particular, but there are very specific requirements to hardware that's sent into space.

I'm using the Mars Science Laboratory as an example here:

The MSL uses twin PowerPC RAD750 boards. If one of them fails, the rover could use the other as a backup. After all, you can't go out to Mars to fix a firmware update gone wrong. :) The RAD750's are hardened against radiation in space, and can withstand extreme temperatures. They run at about 200Mhz, and cost around $200.000 a piece. [1] [2]

It runs the realtime operating system VxWorks, which also happens to be what Apple uses for their Airport routers. :) [3]

NASA uses C as their main language, with specific coding standards. [4]

[1] http://en.wikipedia.org/wiki/Mars_Science_Laboratory#Rover [2] http://en.wikipedia.org/wiki/RAD750 [3] http://www.extremetech.com/extreme/134041-inside-nasas-curio... [4] http://lars-lab.jpl.nasa.gov/JPL_Coding_Standard_C.pdf

stinos2• 12 years ago

If one of them fails, the rover could use the other as a backup

Any idea how that works practically? I mean, there are two boards and one set of peripherals. Is there like an external controller which constantly checks if board A is doing fine, and if not, somehow reroutes all peripheral communication to board B?

RoseO• 12 years ago

Philae runs on an RTX2010 microprocessor: http://en.wikipedia.org/wiki/RTX2010

justsee5• 12 years ago

As late as 12 November, the ESA's own FAQ [1] was stating that Philae's minimum mission target was one week of surface operation (powered entirely by primary batteries), with even more operational time powered by back-up batteries (themselves recharged by solar) - resulting in an expected surface operation period measured in months.

They airbrushed the FAQ on 12 November to remove mention of the minimum one week mission target, and inserted among other things '2.5 days'. [2] A diff of the two versions would probably be interesting.

Now with the lander mission prematurely ended an associated scientist is tweeting a very rosy summary [3]:

"What a perfect ending. All the science completed, data received. Primary mission successful. Well done everybody."

How can a week of carefully-planned scientific activities be 'completed' in only 2.5 days? It seems implausible.

How did the primary and secondary batteries not power the lander for the calculated one week+ of operation?

Why aren't they open about what clearly seems to be a major failure with the scientific mission?

It seems a case of intense bureaucratic / political pressure to change targets after they aren't met, and the fact scientists are participating in this is pretty disappointing.

[1] https://web.archive.org/web/20140805030451/http://www.esa.in...

[2] http://www.esa.int/Our_Activities/Space_Science/Rosetta/Freq...

[3] https://twitter.com/rocketeddy/status/533421309553016832

acqq21• 12 years ago

The targets have to change during the mission. The initial plan was even the another comet. It shouldn't matter.

http://en.wikipedia.org/wiki/Rosetta_%28spacecraft%29

"Rosetta was set to be launched on 12 January 2003 to rendezvous with the comet 46P/Wirtanen in 2011.

This plan was abandoned after a failure of the Ariane 5 carrier rocket during a communications satellite launch on 11 December 2002, grounding it until the cause of the failure could be determined."

No reason to blindly stick to the initial target when you're doing something for the first time ever. It's not that you planned to drive from your home to the shopping mall and have to excuse to your other that you went drinking beer instead. You would probably complain that it's not an initial comet now too?

The device landed on the darn comet! After travelling 6 billion km in 10 years. Managed to work a few days and send the data! First time ever! Powered only by the solar energy! (+) In the outside temperature of absolute zero. How many firsts do you need?

https://www.youtube.com/watch?v=uEY58fiSK8E

Nothing built by humans was ever on the comet surface before. This thing even worked.

+) Edit: Thanks to jdiez17 for pointing that the lander used a non-rechargeable battery on the comet surface. It was all the time planed to do the main work with that battery. The solar powered work wasn't the primary objective.

jdiez172• 12 years ago

To be completely fair, it was not powered by solar energy - the experiments were run on power from the non-rechargeable battery. Which is fine, this is what Philae was designed to do. It looks like they completed all the objectives in the First Science Sequence (FSS), which was the lander's primary mission.

justsee5• 12 years ago

I'm just raising the kind of precise, detail-oriented questions that typically emanate from this community.

Your response relies on an appeal to emotion rather than logic, and doesn't seem particularly interested in engaging with the substance of the questions raised?

jeffdavis• 12 years ago

Historical revisionism is not honest and it raises serious credibility issues.

That's bad for science. It's quite similar to adjusting your hypothesis to fit the data. Not as bad as manipulating the data, but not ethical, either.

danmaz743• 12 years ago

Their mistake was to state a _minimum_ target mission like that in the first place, when you know that this is an incredibly complicated mission.

acqq21• 12 years ago

Even that isn't the mistake at all. It's a good strategy to prepare to do a lot, then when some things go wrong, at least some of all things we're prepared for work. If you set the goals too low, you'll do much less. Therefore, the basic plan was to do the most of the work during a short time period. But they prepared to be able to do something interesting for much longer, if everything goes as perfect as it ideally could.

The mistake would be allowing others to feed on smaller-effect non working stuff instead of the things that amazingly worked.

Osmium• 12 years ago

It seems a case of intense bureaucratic / political pressure to change targets after they aren't met, and the fact scientists are participating in this is pretty disappointing.

This is a big leap to make from the available evidence. Mission targets change all the time. It's a very fluid situation with many unknowns, so I don't find it at all surprising. I think calling foul play is premature to say the least.

justsee5• 12 years ago

Do you think changing the mission target of a 12 year mission on the day of landing has a scientific or bureaucratic / political motive? I'm inclined to believe it is the latter.

Until 12 November the FAQ [1] stated:

During the first week – the minimum mission target – a first run of the most important scientific measurements will be completed. During this phase the lander can operate on primary battery power, should this be necessary. In a second phase that is meant to last up to three months, a secondary set of observations will be conducted, using backup batteries that will be recharged by the energy from the solar cells on the lander. However, no one knows precisely how long the lander will survive on the comet.

Editing to omit the minimum mission target on 12 November [2] indicates something was already wrong at that stage, which would presumably relate to the two batteries that were to power the lander over more than a week, but no public announcement of any issue like that was made. So we should instead assume the batteries were fully operational.

Instead we have ESA announcements and news articles asserting that the reason for the very short period of operation was a lack of solar power, but solar was never planned to be required for over a week at least.

It seems obvious that they had a battery failure. That would not be surprising, but why not openly announce it?

[1] https://web.archive.org/web/20140805030451/http://www.esa.in...

[2] https://web.archive.org/web/20141112043243/http://www.esa.in...

adventured• 12 years ago

The time variance is not very interesting to me at all, but the question of how or if they were able to get at least a week's worth of science done in 2.5 days, is very interesting to me. Was all the science completed, or just a fraction of it? Did they originally plan for only doing a day or two of science (with anything else being a plus), so the short mission life wasn't a problem?

acqq21• 12 years ago

How about first learning which experiments were actually supposed to be done? Can you list them? Can you explain what they are about? Then we can try to consider how much of which of those were done and what are the actual consequences of different schedules in their execution.

We can expect the years of scientific papers based on the analysis of the raw data made by this mission.

avar2• 12 years ago

Here's a word diff between the two FAQ versions you posted: https://gist.github.com/avar/29d060e178e8fac4e2a3#file-faq-w...

Just search for "[-" to find deleted entries and "{+" to find added entries.

Arnt• 12 years ago

They got there, landed and carried out the primary science mission. They didn't even start on the secondary work (AFAICT), but that's called secondary for a reason.

At a guess, the primary science mission was done so quickly because that's what they did. They might have spent more watts on locating the lander, for instance, or on taking pretty pictures.

petercooper• 12 years ago

It seems a case of intense bureaucratic / political pressure to change targets after they aren't met

This is essentially the European Union's modus operandi.

gtirloni2• 12 years ago

It's disappointing that this is the most upvoted comment in this thread. The mission was a success and will enable the scientists to understand much more about the whole thing. Plus, the orbiter will continue to track the comet and there is a chance the lander will come back from hibernation mode once there is more sunlight available.

I think people in general have come to expect the incredible lifetime of the Mars landers as the norm. It's not.

But since this is HN, I'm sure we all in the IT world are pretty confident in our estimations and our projects are a complete success all the time. Might explain why we are so disappointed with ESA. </sarcasm>

turbohz• 12 years ago

Many might not agree with the conspiracy tone of the comment, but we can see that there's something to be explained.

cjensen• 12 years ago

The mission was not a success: it did not meet their minimum goal of one week.

Failure happens and is nothing to be ashamed of when trying for such an ambitious goal. ESA needs to own it and move on.

shiven• 12 years ago

Either I am failing to grasp what you are saying or you are completely naive about the humongous risk involved in cutting edge science of any kind.

This ain't some piddly kickstarter trinket. And exactly what was promised that you didn't get your money's worth for?

Speaking as a researcher in the biological sciences, funded by public tax-payer sources only (don't forget, I also pay taxes), the risk of failure is absolutely astronomical with every project I have ever undertaken. The fact that those projects have succeeded the way they did, is, at least in my mind, phenomenal. Even then, none of these projects, or any projects of any other scientist in my field, have ever achieved all their stated goals.

If this rankles you, move to a place without public funding of science and bet your money on trinkets put up on kickstarter. Or if they are not trinkets, but are true attempts at solving hard problems(curing HIV/cancer, landing on a comet), I hereby guarantee that none of them will succeed 100% of their stated targets.

johnchristopher8• 12 years ago

This ain't some piddly kickstarter trinket. And exactly what was promised that you didn't get your money's worth for?

Parent never stated he wanted his money's worth. He points out some obvious history rewriting which highly harm Science's image (IMNSHO). In no way does that diminishes this mission's outcome, results, feats and the admiration it rightly deserves.

I don't understand the hostility here for a valid question about something that has nothing to do (obligatory political rewriting, maybe ?) with what was achieved.

I hereby guarantee that none of them will succeed 100% of their stated targets.

But you don't lower your expectations after the facts and state "look, we did it as we told we were going to do it".

hueving3• 12 years ago

If a project fails to meet its goals, do you go back after the fact and change the goals or do you admit that you didn't meet them?

Ilverin• 12 years ago

Not directly relevant, but why not spend the minute necessary to google whether the explanation for "How did the primary and secondary batteries not power the lander for the calculated one week+ of operation?" is readily available? (it is:

The harpoons failed to deploy leading the lander to bounce off of its landing target and land in a crater where the solar panels intended to increase its battery life had limited sunlight. http://www.vox.com/2014/11/13/7214941/philae-comet-rosetta

)

justsee5• 12 years ago

1. The primary non-rechargeable battery was designed to power it for a whole week.

2. The secondary rechargeable battery was designed to continue powering it for months after that.

The detail you include is only relevant to 2, and keep in mind it is reasonable to assume that the secondary battery was fully charged before descent.

sailingparrot• 12 years ago

The primary objective was always planned to last few days, and it did that part pretty much perfectly (80-90% of results were received). After these few days, there was a secondary objective, which was to turn Philae into a kind of weather station on a comet, with pretty much every instrument turned off.

It would have been great if it had worked of course, but compared to the main objective it doesn't really matter. What they really want to know is the chirality of the water on the comet and wether or not the comet contains certain elements, it seems like they manage to get this data.

Also the secondary objective is not totally abandonned, since there is still a chance to see Philae back in some months, with the comet getting much more sunlight and warming considerably.

Plans change with time, and the FAQ is adapted to those plan. Hell iirc there wasn't even suppose to be a lander in there initial plan 25 years ago.

melling• 12 years ago

"Why aren't they open about what clearly seems to be a major failure with the scientific mission?"

Human nature. Haven't you worked in a corporate environment where people try to spin to the positive? A lot of money was spent and people want to feel good about the results.

When they sold the project, the PowerPoint needed to present a great show or it wasn't going to get funded. A 1 week minimum was probably needed.

Anyway, I could go on but just try observe human nature, otherwise people will accuse you of being negative.

As for me, I thought it turned out to be a great because it became a mainstream story. We should be putting 4k video cameras on new craft. Get people excited so we can get a budget to build 10 times as many vehicles.

Semiapies• 12 years ago

Bandwidth's surprisingly limited on these missions, so 4K cameras, while awesome, would be problematic.

skywhopper3• 12 years ago

I'm assuming they burned through much of the initial battery charge trying to establish contact, determine orientation, right the lander, etc. So it may have been able to operate for a week had they not had to do a lot of things they hadn't planned on.

Yes, they want to give things a positive spin, but they aren't being disingenuous. They have learned a lot from this, and they got to run tests with all of the equipment on the lander. Calling it a major failure is way off base. You often learn more from things going wrong than from when they go right. Maybe not the things you were planning on learning, but this is very far from a failure.

I also think you're over-interpreting their "minimum mission target". That was an "if everything goes to plan" target. Everything didn't go as planned, but here's the thing: that's also in the plan. It is not possible to do this kind of mission without things going wrong. Usually when things go wrong, you get no data back. But despite the landing going terribly awry, we still got a lot of data back!

If you consider this a failure or a disappointment, then I'm glad you don't work for the ESA. You are far too cynical to be able to get this kind of science done.

mikeash• 12 years ago

Why is this comment at the top? Why do I have to scroll down so far to get to any sort of interesting discussion about the lander? Pathetic.

johnchristopher8• 12 years ago

So I went ahead and actually used kdiff. Here are the relevant passage.

Honestly it looks more like live rewriting of the FAQ to take into account the fact that Philae had a bumpy landing. I don't see an intention to deceive. It's awkward to present the document without mentioning it's not the detailed mission objectives.

That maybe the `perfect ending` considering we have some data back and well.. it's the only ending we have so rosetta exploding before philae could even be launched might have been labeled `perfect` too because it's the first time we put something into the orbit of a duck-like comet.

They certainly wished they had more philae time though. That would have been even more perfect. I wouldn't qualify this a `major failure` though (does the hostility come from that ?).

The science observations will start immediately. During the first week – the minimum mission target – a first run of the most important scientific measurements will be completed. During this phase the lander can operate on primary battery power, should this be necessary. In a second phase that is meant to last up to three months, a secondary set of observations will be conducted, using backup batteries that will be recharged by the energy from the solar cells on the lander. However, no one knows precisely how long the lander will survive on the comet.

And then:

The science observations will start immediately. During the first 2.5 days the first series of scientific measurements will be completed. During this phase the lander will operate on primary battery power. In a second phase that may last up to three months, a secondary set of observations will be conducted, using backup batteries that will be recharged by the energy from the solar cells on the lander. However, no one knows precisely how long the lander will survive on the comet.

skywhopper3• 12 years ago

Having read the two different versions of the FAQ, I also have to dispute your thesis here. On November 12, that FAQ page was probably getting more hits in an hour than it had in its entire history up until then. Say you're in charge of communications, and due to the landing problems, the mission profile has just changed from best-case to medium-case. What's the point of a FAQ that's wrong? The question is "How long will the lander operate on the comet's nucleus?", not "How long did you originally promise the bureaucrats the lander would operate?"

As the answers change, the FAQ page changes. The previous version of that page on the Internet archive doesn't mention the landing at all. So this isn't even a long standing promise. Probably they were making estimates and new guesses every few days as they got closer to the comet and learned more about it. The target mission duration probably depended on the location they landed, which wasn't decided until a few weeks ago. Anyway, the FAQ page is not the official mission planning document, and it's not meant to be a history of every change in the plan. It's a place to answer questions that the public and the press have about the current state of the mission.

TrevorJ• 12 years ago

I read somewhere that the odds they places on getting the thing to stick the landing at all was between 50 and 75%. We put a lander on a comet, I'd be celebrating the upside too if I was them.

Stratoscope• 12 years ago

While you work on those discrepancies, I'm going to enjoy this version of the story and let myself get a little teary-eyed over this astounding success:

@ESA_Rosetta I'm feeling a bit tired, did you get all my data? I might take a nap… #CometLanding
Thank you, @ESA_Rosetta! I did it! I became the first spacecraft to land on a comet & study it! But it’s not over yet… #CometLanding
My #lifeonacomet has just begun @ESA_Rosetta. I'll tell you more about my new home, comet #67P soon… zzzzz #CometLanding

https://twitter.com/Philae2014

MichaelMoser123• 12 years ago

will it get more energy once it gets closer towards the sun? will it still be operational once it gets there?

arrrg4• 12 years ago

It’s an FAQ. It tells you precisely nothing about anything. Don’t be stupid, don’t be conspiracy mongering please. Why is this trash up there? It’s insane that this crap is seen as a valuable contribution.

TillE• 12 years ago

This is the second thread in as many days that's been completely derailed by embarrassing, irrelevant crap. Embarrassing because somehow the comments still have scores over 0.

verytrivial• 12 years ago

I couldn't help but wish there was someone of NASA's calibre with respect to public outreach "handling" this. I really think they got the tone wrong -- 99% of the THOUSANDS of people watching this really just wanted to experience the adventure, warts and all. We know it's hard, we empathise. We wanted to experience the trill, terror and wonder. There really wasn't any need to clam up like they did. If only they had someone (higher profile? I really have been looking for a good feed from with ESA) who could walk around and ask for the pulse of the investigation. "We have no idea, and this is why ..." would still be fascinating. Edit: And I LOVE that NASA just has a raw feed of the images as they come down. I'm thinking of the Mars rovers here. I can't fault how those programmes are communicated.

snowwrestler• 12 years ago

The FAQ on a website is a current document. Once it became clear that only 2.5 days of work was possible, that is the new reality and it is not wrong to update the FAQ to reflect that.

The original mission parameters were well documented--that has not changed because an FAQ was edited. There will undoubtedly be a detailed technical review that investigate every change from plan to execution. Again, a website FAQ is not the forum for that.

jordanthoms• 12 years ago

It appears to be largely political issues that prevented this mission from using a Radioisotope thermoelectric generator , which would have eliminated this particular problem since solar panels would not be required. [1] This is how the Curiosity rover is powered.

If that is the case it's a massive shame - irrational fear of nuclear technology does a lot of damage.

1 - http://www.space4peace.org/ianus/npsm2.htm#2_3

acqq21• 12 years ago

The first (failed) mission to Mars was attempted as early as 1960 by the USSR, continuing with 1964, 1965 Mariner by the US. Rovers came after a lot of previous work done, including a lot of unsuccessful attempts. And the rover weights 900 kg, probably 40 kg of it is the nuclear power generator. Philae is only 100 kg and the first on the comet.

It's certainly not "fear" of the nuclear technology in Europe that prevented something. See for example:

http://en.m.wikipedia.org/wiki/Nuclear_power_in_France

It's that the engineering tradeoffs have to be considered.

guscost8• 12 years ago

While it seems perhaps uncharacteristic of a space agency to make engineering decisions based on politics, if I had to guess I'd imagine that the team was well aware of the PR effect of the power supply chosen for their lander. I would also guess that the same issue was considered at NASA while planning the Mars Exploration Rover (solar) and Curiosity (RTG) missions. Are you claiming that this did not factor into their decision at all?

toddmatthews• 12 years ago

pound for pound, solar power is much cheaper. you cant disregard the weight considerations of a thermoelectric generator

danielweber2• 12 years ago

Yes. I love nuclear, and think we should use a lot more of it both on earth and in space. But for things in the inner solar system not landing on a planet, solar is often the right answer.

fbender2• 12 years ago

(Aerospace engineer/student here)

While there were certainly some political aspects to the question, there were other more pressing reasons to not pursue an RTG design. First and foremost (as others have pointed out) is the lack of knowledge towards this technology within the EU/ESA member states. Also, there's little left of the fuel usually used for these generators (238-PuO2 in space applications), and while it can be bred, none was produced for centuries (last time I checked). It is expected that NASA can only launch a couple of addtional RTG-powered missions before its ressources are depleted.

An RTG also poses quite a few engineering challenges for the spacecraft itself. They are huge and heavy with low efficiency, and their design requires them to be positioned on the outside with sufficient surface area to radiate away their heat. One of their main benefits – almost constant power for a long time – is also their biggest flaw: Their power output cannot be regulated.

While these challenges are in no way unsolvable (they are used both in space and on Earth), they require a certain spacecraft design which makes them unsuitable for many missions. If you take a look at the design of Philae and where it was attached to Rosetta, there is no way an RTG would have fit the design and mission characteristics chosen.

They could have chosen a different design. Though the question is then: Would this have changed anything wrt science output and/or success of the mission? I personally don't think so: An RTG would have increased cost and complexity without a significant impact on science output. An RTG would not have helped with the harpoon and ADS (cold gas thruster) issues which are the primary reasons why Philae landed in the shadows.

Though certainly a malfunction has happened, I do not consider this mission a failure, quite the opposite is true! Due to the hopping, there's a slew of unexpected science data which awaits to be analyzed. Additionally, there's still the chance that Philae may regain enough power once the comet is closer to the sun. Lastly, the primary mission objective – analyzing a comet – is still well underway with Rosetta orbitting Tschurie.

crawshaw• 12 years ago

Happily, Pu-238 is being manufactured again: http://news.discovery.com/space/nasa-plutonium-production-sp...

Another source I read at the time of the announcement said it will take a while to spin up, so there are some mission constraints over the next ten years. A Europa mission would wipe out existing supplies.

tete• 12 years ago

I'm really curious about the results. This is the first time something like this has happened, but with the results, actually knowing a lot of variables, not even from the lander itself other missions will have something to base their work upon.

The first programming languages (static, duck typed, ...), database systems, web frameworks, anonymization frameworks, ... all had a lot of things that were either far from perfect or are now considered stupidity. But when nobody did what you did, when you are a pioneer everyone following would be a fool not to look at your work.

Also a nice example: Operating Systems. In the early days they were considered a waste of energy, time, resources. Why would you want to emulate computers on other computers (no, not visualization, but running multiple programs) or why would you use that valuable memory/storage space to have multiple programs on a machine at once? Those used to be actual questions. But that's a bit far fetched.

The project was/is a real pioneering project and I have lots of respect for people investing all their lives (more than two decades in this case!) so passionately into landing on a comet. Not too long ago that was science fiction.

The first message on the internet (arpanet) was meant to be "login", but it crashed after the o. I think those people got further, even though without doubt it didn't run as hoped for.

erre2• 12 years ago

Rosetta wouldn't have some mirrors, or even reflective surfaces, would it? It could position itself to reflect sunlight onto Philae.

I mean, I'm sure Rosetta has neither (in useful conditions), but there's a thought for next time :/

sylvinus• 12 years ago

This was asked in a French Q&A session with the ESA and they dismissed it as "science-fiction" :)

http://www.lemonde.fr/sciences/article/2014/11/13/philae-peu...

erre2• 12 years ago

Well, I meant it more as "hopeful pondering", but point taken :)

Ono-Sendai• 12 years ago

That would be possible in theory, a few problems though:

You would need a flat surface to reflect light towards Philae, so the only appropriate surface would be the solar panels. The solar panels are not mirrors however, they would probably only reflect about 5%-10% of the sunlight towards Philae. This is even assuming the solar panels are sufficiently flat.

Also the location of Philae is unknown (AFAIK), so there is the problem of where to aim the reflected light.

Finally the relative direction from Rosetta would presumably change as the comet rotates, which means the solar panels or Rosetta as a whole would need to be continuously aimed at Philae, using propellant and/or other energy.

thyrsus• 12 years ago

Apollo retroreflectors.

https://www.xkcd.com/1441/

splitbrain• 12 years ago

I assume that Philae isn't meant to be powered directly by sunlight but has an intermediate battery? So wouldn't it make sense to simply wake him once this battery is full, do some experiment, send the data and go back to sleep until recharged again? Shouldn't that work even with low light conditions, just that the sleep phases would be much longer than planned? The article sounds like they aren't sure Philae will ever wake up again.

acqq21• 12 years ago

The space is unbelievably cold. The lander is in the shade, meaning the temperature there is probably mostly at least around minus 60 degrees. The battery has much higher operating temperature.

waps2• 12 years ago

It's actually unknown whether there's an atmosphere there. Temperature in space is very cold, sure, but if there are no gas collisions nothing carries the heat away (like, say, on Antarctica). So the lander would only really be cold where it touches the comet, and the comet actually gets quite hot at times. Wikipedia mentions that Haley's comet was 70 degrees celcius (above zero) last time it passed by Earth.

Despite geostationary satellites operating in an environment that's nominally -265 or so degrees celcius, the problem they usually experience is overheating, not freezing. Blackbody radiation will eventually carry the heat away, but we're talking decades to get to -100 or so.

For instance, a human body at rest generates about 150 watts of power, which would kill you in geostationary orbit without a cooling system. It would kill you because it wouldn't take long for your body temperature to rise to 52 degrees, at which point your cell metabolism abruptly stops (your mitochondria will stop generating energy). It would take longer than it takes you to choke though. Though nobody's ever tried for obvious reasons, you should be able to exit a space station and get back in with just a helmet that protects your mouth and nose and ears from decompression. You wouldn't freeze, you wouldn't explode. You'd overheat in 10-15 minutes or so. If you survive that, you'd die 2 weeks later from radiation poisoning. On the moon you need heating, because it actually has an atmosphere that would carry heat away.

It is fun reminiscing about just how special our place in the universe is. Human bodies wouldn't be able to survive on planets 30% closer to the Sun, or about 15% farther away. We wouldn't be alive without a mostly oxygen atmosphere, because without the ozone layer, solar radiation would kill us. Without the earth magnetic field, solar radiation would kill us. Without the sun protecting us from interstellar radiation, we'd die. If our solar system was further to the outside of the milky way, we wouldn't survive the radiation, solar protection or not. If it was closer to the middle, we wouldn't survive. It's unknown whether it's a black hole at the center or something else, but it sure outputs a lot of radiation. Oh, and we're in the < 0.1% of the milky way that hasn't experienced a supernova explosion for about 3 billion years (a supernova explosion at 20 lightyears or less would kill all life on earth. 50 lightyears is considered the minimum safe distance for large mammals to survive). The milky way has collided with at least 3 other (tiny) galaxies, none of the collissions were (are) anywhere near us, as the tidal stresses would alter planetary orbits, and so on and so forth.

All of this is ignoring the physical necessities for life to exist. If the fine structure constant, for instance, was 0.1% bigger or smaller, there would be no chemistry, and no humans. If the speed of light was ~5% bigger or smaller, there would be no atoms, as there would not be any stable electron orbitals, and so on.

ajuc• 12 years ago

Battery can't be charged in low temperatures. It has to be heated to 0 C to be charged, and there may be not enough energy to do that in the short period that the sun reaches solar cells.

Gravityloss2• 12 years ago

I wish there were a lot more of missions like these. We should accept some failures as well. If the cost can be lowered, the increased risk can be offset by more tries. It's better for the science as well if the missions are more diverse and the lead times are shorter.

I hope humanity grew up, so that failures would not produce so much backlash. Seems everybody feels so entitled in this age.

CoolGuySteve• 12 years ago

I'm sure they figured this out and decided against it, but I never understood why they often only send 1 device on missions like these. I understand launching things is very expensive, but you'd figure the R&D and risk associated with failure would cost much more.

Monotoko• 12 years ago

Aye, most of the work is already done. I'm sure a second one could be launched at a fraction of the cost.

danielweber2• 12 years ago

It's hard to wow the governments with "we are going to do the same thing again, much cheaper." Even though it's the good way to get the most science bang for buck.

Gravityloss2• 12 years ago

It's not common, yes. Spirit and Opportunity come to mind.

Mars Express and Venus express were based on similar hardware.

guscost8• 12 years ago

This was a very interesting mission, and sticking the landing alone means that it was a success.

Well done, let's hope some interesting data was collected as a bonus.

guelo• 12 years ago

Is that a grammatically correct contraction for "Our lander is asleep"?

dang2• 12 years ago

Yes.

justsee5• 12 years ago

Hey dang - I noticed the comment below I made which stuck to the top for most of this thread's life dropped to the bottom at the time you commented here.

What's the process for penalising posts in this situation?

Is it just an individual decision where you've decided it distracts from a valuable discussion?

I see I could have been a little less harsh with the damnning commentary (only to a point), but ultimately if we're all scientifically-minded then knowing that the internal targets were airbrushed for the public is a bit of a cerebral 'what?' I'd expect we're down with exploring on HN.

ForFreedom• 12 years ago

We shot that fridge from earth and guided it for 10 years and prior to launch we had it in planning for another 15 years or so to have a battery depletion on the second day?

Why didnt they just use nuclear energy?

Our lander’s asleep

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